Array antennas may have subapertures, i.e. small groups of elements, embedded in the main aperture which have some of their received energy sent to a separate (from the main) receiver channel for a special use such as a guard channel. In many cases, an RF coupler in the feed network diverts a small amount of the subaperture receive energy to the special use channel without significantly affecting the main channel. The subaperture may have too little receive gain and too high a noise figure for some purposes.